The objects of this proposal are the isolation, characterization and reconstitution of the subunits of the R. rubrum coupling factor (ATPase) and transhydrogenase factor (TH) in order to understand the structural organization of these complex proteins and to relate structure to functional organization on the membrane. Arylazido-beta-alanyl photoaffinity analogues of ATP, ADP, NAD ion and NADP ion developed in this laboratory shall be used together with a variety of physiological and nonphysiological conditions to bring about specific and irreversible interactions between the above proteins and these nucleotides. In R. rubrum chromatophores the exergonic hydrolysis of ATP catalyzed by the coupling factor ATPase is one of the methods utilized to drive the energy dependent transhydrogenase reaction, NADH plus NADP ion yields NAD ion plus NADPH. Because of this the reconstituted energy dependent transhydrogenation can be used to evaluate the effect of specific modifications of the coupling ATPase on the ability of the membrane system to drive energy dissipative (i.e. energy requiring) reactions. In a similar manner photophosphorylation, which also requires the participation of the coupling factor, will be used to monitor the membrane potential for energy conservation as a function of coupling factor modification.